Failure Investigation and Sustainable Renovation for Slope at National Chi Nan University in Taiwan

Abstract

On September 21, 1999, at 1:47 a.m., Taiwan was shaken by a magnitude 7.3 Chi-Chi earthquake, the most severe one on this island in the past 100 years. The National Chi Nan University (NCNU), located in Puli, Nantou County in central Taiwan, suffered a significant landslide because it is in the worst-hit location and with the worst geological structure. During the earthquake, a massive amount of soil collapsed from a slope that measures 250 m in width and 80 m in height, blocking the entrance to NCNU completely. A failure investigation and dynamic simulation of the reinforced slope/wall were conducted by the finite element software PLAXIS with the time history of acceleration recorded near the site during the Chi-Chi earthquake. The seismic source is assigned on the lower boundary of the finite element mesh. The Mohr-Coulomb constitutive model is used for geological materials. The results indicate that the soil mass and reinforced slope/wall above the weak boundary moves at a greater scale compared to that below the dip plane. The principal directions of displacement of the mesh above and below the dip plane are different, which also indicates that the simulated failure plane occurs along the dip plane. For renovation work, instead of using the traditional concrete structures, the designer, in consideration of environmental sustainability, adopted some green measures. The measures included roadway alignment adjustment, soil nails, a vegetated reinforced soil slope/wall with wraparound facing, and geoweb with vegetation. Completed in 2002, this project withstood several major typhoons and earthquakes in the past 17 years. It has been proved successful in terms of sustainability factors, such as safety, durability, reliability, ecology, landscape, reduction of waste, and carbon emission.